Pile driving system and apparatus

ABSTRACT

A system for driving piles by a succession of blows struck from above by a hammer element wherein a driving head assembly transfers the blows to the upper end of a hollow elongated pile. The hollow pile entraps a water column beneath the head and means are formed in the head for transmitting portions of the water column via the head in response to blows struck upon the head. A cushion of entrapped gas is disposed between the head and column of liquid to momentarily absorb reactive forces derived from the column of water.

[451 Aug. 1, 1972 United States Patent Doughty 541 PILEDRIVINGSYSTEMAND948,989 2/1910 Coffey............................173/86 APPARATUS1,938,459 12/1933 McNeilly........................173/86 2,342,2532/1944 Cooley............................173/88 [72] Invent mughty2,721,055 10/1955 Madson et al. ...............175/293 [73] Asslgnee:222:: g: a 82 Corporatmn Primary Examiner-James A. Leppink p gAttorney-Hem, Hohbach, Test, Albritton & Herbert Dec. 28, 1970 Appl.No.: 101,458

[22] Filed:

[57] ABSTRACT A system for driving piles by a succession of blowsRelated U.S. Application Data Division of Ser. No. 756,685, Aug. 30,1968 Pat. No. 3,604,522.

struck from above by a hammer element wherein a driving head assemblytransfers the blows to the upper end of a hollow elongated pile. Thehollow pile entraps a 'water column beneath the head and means areformed in the head for transmitting portions of the water column via thehead in response to blows struck upon the head. A cushion of entrappedgas is disposed between the head and column of liquid to momentari- 7097 70 7 l l /7 8 .8 3 3 1. 21 I7 5 M 6 "O m ma. 3 WHH U W16 .6 m m. IN Nmmm6 v 0/ ""5 7 "0 "T UhF ly absorb reactive forces derived from thecolumn of water.

[56] References Cited UNITED STATES PATENTS 5 Claims, 8 Drawing Figures863,614 8/1907 Zake.................................l75/6 SHEET 1 OF 3Samuel Clifford Doughtyf ir f' PATENTEDAUG 1 I972 a in W INVENTOR I(V112: ATTORNEY PATENTEnAus H912 3.680.644

SHEET 2 BF 3 I 77 9 r mvENfoR 1) Samuel Clifford Doughty m4, M M

ATTORNEY w v fl 3 04 54 w z lll/l fifl Samuel Clifford Doug y Attorneys14/ A 9 MW PATENTEDAuc 1 1912 SHEET 3 (IF 3 PILE DRIVING SYSTEM ANDAPPARATUS CROSS-REFERENCE TO RELATED APPLICATION This application is adivision of my application U.S.

Ser. No. 756,685, filed Aug. 30, 1968, entitled Pile 5 Driving Systemand Apparatus, now US. Pat. No. 3,604,522 and copending herewith.

BACKGROUND OF THE INVENTION This invention pertains to a system fordriving piles by a succession of blows struck from above by a hammerelement and to apparatus for use in such systems. This invention isparticularly useful in driving piles into the ocean floor under greatdepths of water, though not limited exclusively to such application.

In the construction of off-shore drilling platforms and other platformslocated well out into the ocean,

significant overturning forces of wind and sea are experienced by theplatform and its supporting tower structure. Typically, in suchoff-shore platforms, a tower supports the platform or superstructurefrom the ocean floor by means of a number of elongated hollow legsextending downwardly from the superstructure. The downwardly extendinglegs form the so-called jacket or support tower structure for theoff-shore platform.

It is necessary to resist overturning forces of wind and sea as well asother overturning forces. This, in the past, has been done by means ofproviding elongated piles which penetrate to great depths and to whichthe tower can be secured by means of locating the piles coaxially of thehollow legs of the tower.

In order to drive piles coaxially of such jacket legs at greater andgreater depths, it is becoming increasingly necessary to apply greaterand greater hammering energy to the pile, preferably from theconvenience of outdoor work stations rather than from submarinelocations. It has been observed that losses in the transmission ofenergy can occur where a pile extension is disposed atop the upper endof the pile to permit the blow to be struck at such an outdoor workstation above the surface of the ocean. Certain follower mechanisms havealso been employed but are also believed to suffer from the samedisadvantage. However, in order to employ larger and larger hammerelements or rams for striking the pile and for other reasons, andnotwithstanding the inherent energy losses, it has remained preferableto drive the pile from the outdoor work station rather than to insertcompressed air and steam hammers down into the leg of the towerstructure for operation below the surface of the water.

Thus, while it is desirable to transmit the hammer energy substantiallydirectly to the pile without loss of energy and by extremely massivehammer elements which can be readily operated from the outdoor workstation at the top of the tower or on the platform supported by thetower, these objectives have been somewhat incompatible.

Where underwater steam and air hammers have been attempted for use atsubmerged locations within the tower legs, trouble has been experiencedin discharging the exhaust of such devices into the air above the watersince this is usually done by carrying a heavy hose downwardly throughthe water and coupling it to the hammer. This hose must be very strongto overcome the tendency to collapse under high external water pressure.Other difiiculties to be overcome are condensation of both live andexhaust steam when carried to great depths through cold water, wherebythe hammer mechanism tends to become drowned in a pocket of watercondensate which impairs its functioning.

Other difficulties in the past have stemmed from the presence ofinfiltrated water under high pressure finding its way into the casing soas to come between the contacting surface of the falling rarn or hammerand the top of the driving block or anvil which transmits the blow tothe pile. Any such intrusion of water, in view of its incompressiblenature, greatly dissipates the energy of the blow of the harruner andrenders it significantly less effective. Such water intrusiondifficulties in the past have been countered by introducing compressedair into the casing so as to provide sufficiently high pressure to driveout the water. However, difficulties have impaired the drivingefliciency of underwater hammers of this type. Furthermore, suchunderwater hammers have seldom been used at great depths of water, forexample, at depths appreciably exceeding more than a hundred feet.

In circumstances such as the above off-shore support tower applicationwhere it is found necessary to drive piles below water level and wherethe piles are hollow, it has been observed that the column of waterentrapped within the'pile can rise to a point where the anvil element 21acts directly against the column of water and thereby generates acompression wave, in the nature of a water hammer, capable of doingconsiderable damage due to the great forces developed by such wave.

OBJECTS It is, in general, an object of the present invention to providean improved pile driving system and improved apparatus therefor whichovercomes the foregoing and other problems.

It is another object of the invention to provide an improved piledriving apparatus wherein reactive forces derived from a column of watercaptured within the pile being driven are dissipated without substantialloss of energy from the pile driving blow.

These and other objects of the invention will be more clearly understoodfrom the following detailed description of preferred embodiments whenconsidered in conjunction with the accompanying drawings and generalsummary of the invention.

SUMMARY OF THE INVENTION In a system for driving open, hollow piles,there is provided, in general, in combination with the piles, a drivinghead for transmitting the blows of a hammer to an end of the pile. Thedriving head includes an anvil portion adapted to transmit the blows tothe pile to move the pile toward a water column entrapped within thepile, and means for venting entrapped portions of the liquid of thewater column from within the pile in response to the hammer blows.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an elevation schematic viewshowing an offshore oil drilling platform of the type referred to above;

. system and apparatus;

FIG. 3 isa section view taken along the line 3--3 of FIG. 2;

FIG. 4 tically shows a system for operating the actuator means forproviding a drop hammer action;

FIG. 5 is an enlarged detail view, in section, of a driving head memblyaccording to the invention;

FIG. 6 is an enlarged detail view showing an improved pile constructionaccording to the invention;

FIG. 7 is an elevation view showing another embodiment according totheinvention; and

FIG. 8 is an enlarged section view of a detail portion of FIG. 7. I

I DESCRIPTION OF THE PREFERRED EMBODIMENTS As noted above, the piledriving system as disclosed herein may be advantageously employed inoff-shore pile driving rigs of a type, for example, as shown in FIG.

1. Thus, the superstructure 11 of the rig is generally legs 14 aregenerally hollow tubular members forming pile guide channels. Tower 13typically is secured to the ocean floor 16 by means of hollow pilescoaxially inserted snugly into the hollow interior of legs 14 so thatthey-may be driven downwardly into the ocean .fioor .to great depths inorder to penetrate well beyond the relatively soft upper material of theocean floor. Piles 17 form a close sliding fit within legs 14.

The upper ends of piles 17 are typically left in place to extendupwardly above the ocean floor 16 an amount sufi'icient to provide thenecessary stability to the rig.

A guide channel, other than legs 13, can, of course, be defined in otherways. For example, in the application of off-shore drillingcircumstances, for example, so-called skirt piles" are driven throughand guided by short tubular lengths secured to the exterior portions ofthe jacket." Further, annular guide rings are sometimes employed incircumstances of the above type wherein several piles are used within asingle leg of the structure.

In view of the fact that the legs 14 and the piles 17 are of relativelylarge diameter, on the order of several feet in diameter, and in view ofthe exceptional length of such piles, for example on the order ofseveral hundred feet, it is highly desirable to the amount of pileextension lodged within the legs 14 consistent with safety to the tower.

Thus, where piles 17 extend the full length of legs 14, it will bereadily evident that a considerable waste of expensive piles 17 hasoccurred in view of the fact that the uppermost portions of such pilesare providing little or no supporting or stabilizing function.

4 Inordertoconquerthisprobleminthepashithas been suggested to employ thepile driving follower or extension, as mentioned earlier, which can bestruck at its upper end in the region of the outdoor work station 5 onplatform 18 where the energy will be transmitted indirectly through thepile extension or follower to the upper end of the pile located welldown in the leg. As noted, these systems have been subject to severeenergy losses in providing such indirect force transmitting means.

Referring to FIG. 2, a pile driving system is shown wherein the upperend of a pile 17 is shown disposed in a hollow leg 14 of support tower13. A driving head assembly l9 comprised generally of those componentsshown in the enlarged detail portion of FIG. 2 is sea in the open upperend of pile 17.

Thus, the driving head assembly comprises an anvil element 21 adapted toengage the upper end of the pile 20 17 in blow-transmitting relation.Anvil element 21 includes a tapered frustro-conical portion 210dimensioned and adapted to fit readily intolthe upper end of pile 17 andto be supported by an enlarged midsection 21b serving to form a shoulder22 which rests upon the upper edge of pile 17. The other end of anvilelement 21 is formed to include a portion 21c of slightly reduceddiameter and formed with atop face 23 to constitute the striking face ofthe anvil element 21 which directly receives the blows of alongitudinally movable ram or hammer element 24, the bottom of which canbe very slightly domed.

Portion 21c serves to plug and seal the lower open end of an elongatedhollow case 26 secured to the upper end of anvil element 21 in a mannerto form an 35 extension of anvil 21 whereby both anvil 21 andcase 26travel together in a following movement as the pile 17 penetrates intothe earth. Anvil 21 and its case'extension 26 fit closely within the leg14 in sliding manner comparable to the sliding fit between pile 17 andleg 14. Anvil element 21 may, for example,"be of solid steel: materialor may be formed in a manner described further below relative to anadditional embodiment pertaining to same.

While anvil element 21 serves to sealthe'lower, end of case 26, theupper end of case 26 is also substantially sealed whereby the interiorof case 26 is subjected to air pressure from an air hose 27' connectedto pressurize case 26 through a compressed air inlet 28. At the pressurefrom inlet 28.

Hammer element 24, as noted, moves through a stroke 31 to supply asuccession of blows against the striking face 23 of anvil element 21. Inorder to eliminate any dissipation of the suiking energy derived fromthe falling hammer element 24 by virtue of any accumulated cushion ofair disposed between the lower end of hammer element 24 and the strikingface 23, as might otherwise form at that location by virtue of theclosely fitted guided relation existing between the periphery of hammerelement 24 within the closed case 26, fluid e means have been formedlongitudinally of the case and hammer for transferring fluid (such asair) therealong during movement of the hammer within the case.

Thus, as shown best in FIG. 3, fluted portions 32 form longitudinallyextending peripheral indentations in the cross-section of hammer element24 in the nature of grooves to provide sufficient clearance to transferany entrapped air at the lower end of the falling hammer element 24 tothe increasing space at the upper end of hammer element 24. In order tomaintain a closely fitting guiding relation between hammer element 24and case 26 to any side movement and undesirable lateral vibrationforces, longitudinally extending ribs 33 are provided. Ribs 33 formedbetween each adjacent pair of fluted portions 32 ride along the interiorwall of case 26.

With the foregoing configuration, it becomes readily possible to employan extraordinary massive hammer element 24 on the order, for example, ofmany thousands of pounds. A hammer element of such scope, if not closelycontained within its guiding case can, of course, cause serious lateralimpact forces acting against and damaging to the structure of thesupport tower 13.

Means for reciprocating hammer element 24 serves to lift it through itspredetermined stroke 31 and then release the hammer element to fallfreely to an advanced position where it contacts the striking face 23.Flexible cable means have been provided connected to the upper end ofhammer element 24 in the form of a flexible steel cable 34 anchored inthe upper end of hammer element 24 by suitable known means for embeddinga cable in a solid steel material. A water-tight packing gland 36located in the upper end of case 26 passes cable 34 outwardly thereof sothat cable 34 is free to move in and out of case 26 to lift and releasehammer 24.

Means for actuating the cable so as to move hammer element 24 betweenlowered and raised positions as well as to continuously pay outadditional cable to operate the hammer at increasing depths as the pilepenetrates the earth includes the structure shown at the upper end ofsupport tower 13.

Thus, at the outdoor work station 18, a work surface or mountingplatform 37 supports hoisting means which serves to pay out and retrieveboth case 26 and hammer element 24 as well as to anchor or hold theupper end of cable 34. Thus, the hoisting means is in the form of anengine 38 of a suitable type readily controllable by an operator orattendant 39. Engine 38 is suitably coupled, as by means of the driveconnection 41, to rotate the Windlass portion 42 of a winch 43. Thus,winch 43 serves to wrap and unwrap cable 34 upon windlass 42.

A pulley 44 formed with a relatively deep sheave groove 46 engages thatportion of cable 34 defined between Windlass 42 and the upper end of leg14. As Windlass 42 is operated in a direction to pay out the cable 34,the air hose 27 may also be paid out accordingly so as to extenddownwardly along leg 14. Air hose 27 is, therefore, conveniently carriedupon a retractable hose reel 47 mounted to platform 37 so as to permitthe air hose to be readily paid out along the other end of reel 47.

The upper end of air hose 27 is coupled to an air compressor 48 carriedby platform 37.

Means for actuating pulley 44 to move between advanced and retractedpositions so as to quickly relieve the tension in cable 34 and permithammer element 24 to fall freely under the force of gravity includes thehydraulically operated actuator 49 (FIG. 4). Actuator 49 is adouble-acting hydraulic piston operated by suitable fluid system meanswhereby lines 51, 52 are alternately and quickly respectively connectedto pressure and exhaust lines of a hydraulic pump 53.

The system shown in FIG. 4 for alternately applying pressure and exhaustto the opposite ends of hydraulic actuator 49 is merely representativeof a number of systems for providing the function of developing a greatforce quickly acting to raise and to lower the pulley 44 through itspredetermined stroke. From the foregoing, it will be evident that, inthe condition shown, the spool style control element 58 serves to couplefluid line 52 to pressure from pump 53 via line 54 while connectingfluid line 51 to exhaust fluid to the pump via line 57. It is to befurther understood, of course, that suitable reservoirs and otherconventional hydraulic system devices may be employed to round out thesystem. The system shown in FIG. 4, therefore, is merely representativeof known systems for quickly and automatically reversing hydraulicdrives.

Means are also provided of a conventional nature whereby as the pistonrod 59 moves upwardly to a predetermined degree adequate to properlylift hammer element 24 to a point of release, the valve connectionsdescribed above with respect to FIG. 4 will be quickly reversed so as toquickly hydraulically drive the piston of actuator 49 downwardly andthereby move pulley 44 rapidly out of the way of the falling cable 34wrapped therearound. Thus, movement of a projecting finger or otherprotrusion 61 carried by rod 59 ulti mately serves to close a pair ofcontacts 62 so as to close the circuit of a power supply 63 and therebyenergize a solenoid 64. As solenoid 64 is energized, it will act againstthe urging of a spring 66 which otherwise serves to urge control element58 to the position shown in FIG. 4.

Thus, when solenoid 64 is energized, it can serve to quickly shiftcontrol element 58 in order to reverse the hydraulic connections toactuator 49'.

Having the above arrangement in mind, it is readily apparent that cable34, as trained about pulley 44, forms first and second reaches 34a, 34bthereof. The first reach is directly coupled to move hammer element 24.Hoisting means, such as the winch 43, is coupled so as to anchor the endof the second reach 34b. Actuator 49 is provided with a predeterminedstroke serving to move the pulley from a lower to an upper position inorder to elongate the second reach 34b while shortening the first reachby a multiple of the stroke of actuator 49. In this manner, if thestroke of actuator 49 is on the order of two feet, the hammer element 24will be raised a distance of four feet due to the interposition of therising pulley 44.

Additional multiplication of the actuator stroke can, of course, beobtained by introducing additional pulleys forming additional reaches ofcable 34.

Further, from the foregoing, it will be readily evident that when pulley44 is being retumed, it will have less distance to travel than willreach 34a, and, accordingly, pulley 44 can move to its retractedposition in less time than reach 340 and thereby more quickly relievethe strain on cable 34 to permit hammer element 24 to fall and strikeits blow. It is apparent that pulley 44 only needs to be accelerateddownwardly from its upper position at a rate exceeding one half theacceleration rate provided by theforce-of gravity (acting on the cable34 alone). Thisfraction may be further proportionately reduced byintroducing additional pulleys for further subdividing the cable intoadditional reach p'ortions.

With reference to FIG. 5, another embodiment of the anvilelement 21serves to solve the problems of entrapped water columns as noted at theoutset above whereby shock waves and water hammer effects may becreated. Accordingly, an anvil element 71 includes a striking face 72 atits upper end adapted to be struck by the hammer element 73. The lowerend of anvil element 71 includes a hollow recess 74 containing aninflated gas-filled bladder 76. Bladder 76 may, for example, be aninflated nylon-neoprene hollow sphere havingan outsidediameter on theorder of one foot or greater and a suflicient capacity so that it can beinflated with air, for example, to accommodate not less than thehydrostatic head developed at the top of the submerged pile for theultimate depth to which the pile is to be driven.

"Thus, if anvil element 71 is directly engaged on the upper'end of thethickened wall portion 77 of a pile 78 and the water level has risen toa point where it may make direct contact with the exterior of bladder76, the striking blow of hammer 73 will not transmit a shock wavethrough the liquid medium within pile 78 in view of thefact that thecompressive air within bladder 76 serves to initially absorb the shock.

. The striking blow will, of course, serve to drive the pile 78downwardly somewhat and this can serve to develop additional compressionby virtue of the upwardly displaced column of water contained therein.In order to vent this water column from within pile 78,

flow passages 79 of substantial diameter, for example, on the order of 4or inches, and of a suflicient number are provided so as to quickly ventthe liquid. In the event that the flow passages 79 are incapable ofventing I I the liquid quickly enough to preclude the development of ashock wave inthe liquid within pile 78, it will be readily apparent thatbladder 76 will absorb the momentary increase in pressure and therebyprovide additional time for discharging the liquid without forming thecompression wave.

Another embodiment for safeguarding against the development of acompression wave and for venting the water displaced by downwardmovement of the ho]- low pile is shown in FIG. 6.

Thus, a pile construction 81 has been provided comprised of an elongatedrigid hollow member 82 adapted to be driven in an upstanding orientationby a succession of blows applied at the upper end thereof. The upper endhas been prepared with a thickened wall portion 83. A closure plate 84serves to seal the upper end of pile 81 so as to entrap a cushion of airin the region 86 when lowering pile 81 into a body of water for driving.Openings 87 are formed at a predetermined displacement beneath closureplate 84 so as to vent the column of water 88 in response to compressionderived from the driving blows of the hammer element 89 as the pilemoves downwardly into the earth. The cushion of air in the region 86therefore serves to momentarily absorb the reactive forces of the columnof water 88 formed by openings 87 Y and topermit the flow to vent thecolumn.

In another embodiment of the system for piles, as shown in FIGS. 7 and8, a support tower extension structure 91 supports the hoisting meansand actuator structures described above at an elevation above Hammerelement 94 is designed to strike blowsupon Y the upper end 96 of a pile97 and includes an elongated guide stem portion 98 movable in slidingrelation coaxially within pile 97 and further includes a massive head.

portion 99 formed on the upper end of stem portion 98.

The underside of head oi-son 99 projects laterally to fonn a shoulder101, which moves through a predetermined stroke S, to strike the upperend 96 of pile 97 in driving the pile. A fluid 102 extendslongitudinally of guide stem 98 for relieving or venting fluid surgeduring the striking movement of hammer element 94.

Thus, as in the case ofdriving piles deeply into the ocean floor at aslight slant, batter piles can be driven by the drop-hammer system asdescribed above whereby the hammer is lifted and released from anoutdoor work station and the hammer can strike the upper end of the pileas contained in a leg 103 or other means defining a channel in which toguide and lodge the piles 97.

As thus provided, the embodiment described lastly above provides theadvantage of ,a drop hammer acting against the upper end of a pilebeingdriven, while at the same time serving to permit the pileto bedriven into the earth at a substantial angle to the vertical.

While the systems disclosed herein overcome the problems involved inusing pile extensions and followers, it will be readily evident that thedisclosed.

1. In a system for driving an open hollow pile by a succession of blowsapplied by a hammer from an end of the pile with the pile in a body ofliquid subject to entrapment of a column of the liquid within the pile,a driving head disposed in blow-transferring relation to the end of thepile, said driving head including an anvil portion adapted to be struckby the hammer to move the pile toward the liquid column, and meanscapturing a cushion of gas between said anvil and the column of liquidto absorb reactive forces derived from the column of liquid.

2. In a system according to claim 1 wherein the last named meanscomprises a compliant bladder filled with a compressible gas andinterposedbetween said head and said column in exposure to said column.

3. In a system according to claim 1 further including flow passagesbetween the last named means and said column of liquid for venting saidcolumn of liquid therethrough in response to blows struck by the hammer.

4. A pile construction comprising an elongated, rigid, hollow member,open to receive a column of water therein, and adapted to be driven inan upstanding orientation by a succession of driving blows applied atthe upper end thereof, a closure formed at the upper end of said memberto entrap a cushion of air therein when lowering said member into a bodyof water for driving, openings formed to vent said column of water fromwithin said member in response to compression derived from the drivingblows, said cushion serving to momentarily absorb reactive forces ofsaid column of water to permit the opening to vent said column.

5. An open, hollow pile of a type to be driven in a body of water,subject to entrapment of a column of the water within the pile, by asuccession of blows applied from an end of the pile, 96 a driving headfor transmitting the blows to said end of the pile, said driving headincluding an anvil portion for transmitting the blows to move the piletoward the water column, and means for venting entrapped portions of theliquid of the colunm from within the pile in response to the blows.

$222 83 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent no;3,680,644 Dated I A ust 1 1972.

Inventefls) Samuel Cli ffbrd Doughty- It is ceftifie'd that errorappears in fh e above identified .pzitentgand that-said Letters Patentare hereby corrected as shown below z' H I Co'iux n n 10, line-j 7, afte i: "pile delete "96",

I Signed a nd jse led "this 26-thday of-December 1:97P

(SEAL) Attest:

EDWARD IM.FLETCHER',JR. I l v C ;1 o131-3R-l' GOTTSCHALK v Atte stin'gOfficer 7 1 I 'I Commissionerpf Patents;

1. In a system for driving an open hollow pile by a succession of blowsapplied by a hammer from an end of the pile with the pile in a body ofliquid subject to entrapment of a column of the liquid within the pile,a driving head disposed in blowtransferring relation to the end of thepile, said driving head including an anvil portion adapted to be struckby the hammer to move the pile toward the liquid column, and meanscapturing a cushion of gas between said anvil and the column of liquidto absorb reactive forces derived from the column of liquid.
 2. In asystem according to claim 1 wherein the last named means comprises acompliant bladder filled with a compressible gas and interposed betweensaid head and said column in exposure to said column.
 3. In a systemaccording to claim 1 further including flow passages between the lastnamed means and said column of liquid for venting said column of liquidtherethrough in response to blows struck by the hammer.
 4. A pileconstruction comprising an elongated, rigid, hollow member, open toreceive a column of water therein, and adapted to be driven in anupstanding orientation by a succession of driving blows applied at theupper end thereof, a closure formed at the upper end of said member toentrap a cushion of air therein when lowering said member into a body ofwater for driving, openings formed to vent said column of water fromwithin said member in response to compression derived from the drivingblows, said cushion serving to momentarily absorb reactive forces ofsaid column of water to permit the openings to vent said column.
 5. Anopen, hollow pile of a type to be driven in a body of water, subjEct toentrapment of a column of the water within the pile, by a succession ofblows applied from an end of the pile, 96 a driving head fortransmitting the blows to said end of the pile, said driving headincluding an anvil portion for transmitting the blows to move the piletoward the water column, and means for venting entrapped portions of theliquid of the column from within the pile in response to the blows.